Here’s one way to solve global warming: Spend $90 trillion (£59 trillion) over the next few years to redesign all the cities — as in all the cities on Earth — so people live in more densely packed neighbourhoods and don’t need cars.

That is one of the more ambitious (and possibly outlandish) ideas knocking around the World Economic Forum at Davos, Switzerland, this morning. The Davos meeting is the annual conclave of the world’s ruling class: presidents and prime ministers, CEOs, and religious figures (and the thousands of journalists who follow them, hoping for a soundbite or two).

The $90 trillion cities proposal came from former vice president Al Gore and former president of Mexico Felipe Calderon, and their colleagues on the The Global Commission on the Economy and Climate. That group hopes to persuade the world’s leaders to do something about humanity’s suicidal effort to heat the Earth’s climate.

Part of fighting climate change will mean redesigning, or building anew, towns and cities without cars, Calderon says.

“We cannot have these cities with low density, designed for the use of cars,” he said. “We recommend those cities should have more density and more mass transportation.” Together with a programme for reforming land use, and bringing deforestation to zero, the total cost of this plan would likely be $90 trillion in future investment, Calderon said.